I always thought that it would be Jade Version, considering that both Pokemon Diamond and Jade Versions were fake Pokemon games back when Gold, Silver, and Crystal were out. Or earlier. Upon making a Diamond Version, I immediately thought that Jade Version would be a soon-to-come expansion title.

Dunno what it would be called but I could see two new versions coming out. One of them has Mew on It and the other has a Arceus on it. Maybe Arceus would be Shadow version and Mew would be Light version? Oh, I'm just getting myself confused.

well, personally, I think it'll be along the lines of darkness for girantina. But I can't think of a dark gem...obsidian? I don't know. What my friends and I like to fantacise is that the expansion will be called Platinum version, and includes every region and pokemon.